I finally took the time to fix the sticking exhaust valve that has been affecting me for over a year. Let me preface before I go on that I am not a mechanic. I have never torn into an engine like this to fix anything, but tried it due to the help I've gotten here. Before I took the head off I tighten the head bolts to see if any would move and to my surprise 2 of them did. The 2 bolts between the piston and exhaust valve moved slightly (I didn't tighten hard). You can see in the pics when I got the head off there was actually a leak at those 2 bolts. The head gasket was starting to erode at the leak.
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I checked out the bore and it was fairly smooth aside from this imperfection. According to Jonathon it could be totally benign and I haven't notice anything up until this point to beleive otherwise.
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This is the exhaust valve before and after cleaning.
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This is the intake valve before and after.
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Here is the head and combustion chamber after cleaning, they're not perfect, but I ran out of elbow grease.
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I used laquer thinner and scotch brite pads to clean everything, the brass brushes I got were useless. To clean the valve guides I cut a strip of scotch brite pad, wet it with wd 40 and pushed it into the guide with a copper wire. I used the pad to "floss" the guide clean. After cleaning the piston, I noticed it was dragging when I spun the engine so I put some engine oil on the cylinder walls and spun it around a few times. A few min later I spun it again (was reinstalling valves) and noticed a lot of gunk left behind when the piston went down. Apparently the rings trapped all the dirt from cleaning the piston and the oil was pulling it from the rings. I wiped the cylinder clean, reapplied new oil spun the engine and cleaned again. I did this 4-5 times untill it stopped leaving dirt behind. I oiled the valves also before reassembly using the "2 screwdriver method".....I think that is an inside joke you engine guys have to mess with us newbies. What a nightmare, it takes 2 screwdrivers, 2 hands and a knee to install those damn keepers. If anyone is new to valve work I recommend a valve spring compressor tool!
After reassembly I torqued the head per the manual sequence then went to 35 ft-lbs that I've seen Don recommend on other posts. Since the carb was off I opened it up and sprayed it out with carb cleaner and air. Not an actually cleaning, but was more interested in seeing what it needs, a throttle shaft bushing is in its future. Put the carb on and it fired right up, slight smoke after the first minute from the wd 40 in the muffler. I drove it to the garage at idle so I could change the oil. Then I ran it at 1/2-3/4 throttle for 35 min and retorqued the head, only 3 bolts moved maybe couple degrees. Its running great and the exhaust doesnt stink like it used to! We'll see next week how it handles cutting the grass in the heat, but hopefully no more stuck valve!
Bill